So I recently got total war medieval2 on mobile but I realized multiple problems that I'm not sure how to do.(note I'm on mobile)

1.how to use pikes

When ever I used pikes they'll be useful for like 3 seconds cause after a while they broke pike formation and start using their swords same thing while in defensive formation.than sometimes when holding choke points with them calvary would sometimes literally push the pikes to the side almost taking no casualties sometimes .is this only for me or is their a solution to the problem.also if I put them in defensive formation does it hurt their combat.

2.2 handed unit.ive only heard rumors but are 2 handed weapons unit bugged I'm not pretty sure I haven't noticed anything but it is my first total war game I've played so I'm not sure how good they should be.

3.can you place siege machines on walls.

4.what unit can place fortifications.

5.can rifle unit fire off walls.

6.scotish general like to be dismounted but how to dismount troops I'm not sure how?

7.just any advice a noobie like me wouldn't understand